1. Field of the Invention
The present invention relates to a data reading apparatus for reading data recorded on a data recording part of a film cartridge.
2. Description of Related Art
In recent years, camera conforming to a new photographic system called the Advanced Photo System have been coming in the market. The film cartridge for use with such a kind of cameras is provided with a data disk which rotates integrally with a spool shaft disposed within the film cartridge. On the data disk, there is formed a bar code representing a variety of kinds of information concerning a film contained in the film cartridge (film sensitivity, number of exposable frames, etc.).
The bar code formed on the data disk is composed of, as shown in FIG. 21, a data part (a predetermined series of groups of information) in which a xe2x80x9cWIDExe2x80x9d pattern having a relatively wide width and a xe2x80x9cNARROWxe2x80x9d pattern having a relatively narrow width are alternately arranged in plural, and a quiet zone which indicates ends of the data part.
When the film cartridge is loaded into a cartridge chamber of the camera, a control part (not shown) of the camera causes a drive source, such as a motor, to rotate the spool disposed within the film cartridge, reads information concerning the film from the bar code on the data disk by means of a reflection-type photo-sensor mounted inside the cartridge chamber, and uses the information concerning the film for controlling the subsequent operation of the camera.
By the way, in the new photographic system, there is a standard concerning a stop position of the data disk to determine whether a usage state of the film cartridge as loaded is an xe2x80x9cunusedxe2x80x9d state or an xe2x80x9cexposedxe2x80x9d state, prior to reading of the bar code information. Accordingly, prior to reading information on the bar code, it is necessary to, first, determine the usage state of the film cartridge. Hereinafter, to determine the usage state of the film cartridge is referred to as the DEP determination.
In the conventional cameras, as shown in FIG. 22, the motor is reversely rotated from a point of time t1 when the film cartridge has been loaded, and, then, the DEP determination and the reading of data disk information (bar code information) are performed. After it is confirmed that these operations have been performed normally, an operation of sending the film out of the film cartridge is performed.
As is understandable from FIG. 22, a point of t3 when an area corresponding to the quiet zone has completely passed the position of the photo-sensor is set as a reference timing, and the number of changes of the output (output pulses) of the photo-sensor occurring from the point of time t1, which is the start point of rotation of the data disk, to the point of time t3 is counted. On the basis of the thus-obtained count value, the initial stop position of the data disk is determined.
Then, the output signal of the photo-sensor obtained from the point of time t3 onward is watched, and a time interval at which the state of the output signal of the photo-sensor changes is measured by means of a timer counter or the like, whereby a discrimination between the xe2x80x9cWIDExe2x80x9d pattern and the xe2x80x9cNARROWxe2x80x9d pattern on the data disk can be made.
In the conventional cameras having the above-described arrangement using a single photo-sensor, it is necessary to cause the data disk to make one rotation including the quiet zone, in order to read information on the data disk.
Further, at the time of reading bar code information on the data disk with the data disk rotated, it is generally necessary that the rotation of the data disk is stable. If the rotation of the data disk becomes unstable due to a mechanical disturbance, such as vibration or impact, the reliability of data reading is remarkably lowered. Thus, a code of the xe2x80x9cNARROWxe2x80x9d pattern may be erroneously read as a code of the xe2x80x9cWIDExe2x80x9d pattern. Also, in a case where a dust or the like, which has temporarily adhered to the surface of the data disk, suddenly disappears from the surface of the data disk due to the rotation of the data disk, there is a possibility that it is impossible to read the bar code information normally.
In order to prevent such lowering of the reliability of data reading, in general, information on the data disk is made to be read a plurality of times, and a plurality of results of data reading thus obtained are compared for verification.
However, in the above-described arrangement using a single photo-sensor, the data disk is caused to make one rotation for one time of reading. When reading is performed a plurality of times in order to improve the reliability of data reading, the data disk has to be rotated a plurality of times, too. In the case of the example shown in FIG. 22, reading is performed twice. In this instance, if a result of reading for the first time differs from that for the second time, it is necessary to further continue reading, or to stop the operation on the assumption that reading is impossible.
A period of time required for reading information on the data disk, which is included in the period of time from the time when the film has been loaded into the camera to the time when the film has been transported up to a predetermined position for preparation for photography, has a length unable to be disregarded. Therefore, in the case of cameras having the above-described data disk information reading apparatus, it is preferred that the period of time required for reading information on the data disk is short.
In accordance with one aspect of the invention, there is provided a data reading apparatus adapted for a film cartridge having a data recording part provided on a predetermined moving member, the data reading apparatus comprising a first data reading device which reads data from the data recording part, a second data reading device which reads data from the data recording part and which is disposed at a position different from that of the first data reading device with respect to a moving direction of the data recording part, and a data obtaining circuit which makes a comparison between data read by the first data reading device and data read by the second data reading device and obtains, on the basis of a result of the comparison, data corresponding to data recorded on the data recording part. In the data reading apparatus, a data reading operation on the same data recording part is performed by both the first data reading device and the second data reading device, and results of reading obtained by both the first data reading device and the second data reading device are compared with each other to determine data recorded on the data recording part.
The above and other aspects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.